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Abstract:

A disclosed flow rate control apparatus includes a first substrate, a
second substrate partially bonded to the first substrate, and a
piezoelectric material. The first substrate includes a separation section
separating first and second flow paths in the first substrate, the
piezoelectric material is adhered to an upper surface of the second
substrate above the separation section, and the first substrate is not
bonded to the second substrate near the separation section.

Claims:

1. A flow rate control apparatus to be provided in a middle of a medical
solution injection path from a container accommodating medical solution
into a living body and capable of adjusting a flow rate of the medical
solution, the flow rate control apparatus comprising: a first substrate;
a second substrate, at least a part of the second substrate being bonded
to the first substrate; and a piezoelectric material; wherein the first
substrate includes a separation section having a thickness equivalent to
a thickness of the first substrate where the first substrate is bonded to
the second substrate, first and second flow paths are formed in the first
substrate, the first flow path and the second flow path being separated
from each other by the separation section, the piezoelectric material is
adhered to a position on a surface of the second substrate, the position
corresponding to a position of the separation section, the surface being
opposite to a surface facing the first substrate, and the first substrate
is not bonded to the second substrate near the separation section.

2. The flow rate control apparatus according to claim 1, wherein the
first substrate is made of single-crystal silicon, and the second
substrate is made of borosilicate glass.

3. The flow rate control apparatus according to claim 1, wherein the
first substrate and the second substrate are bonded to each other based
on anodic bonding in an area other than an area near the separation
section.

4. The flow rate control apparatus according to claim 1, further
comprising: a voltage application unit that applies voltage to the
piezoelectric material, wherein duty control is performed by applying a
predetermined voltage by the voltage application unit.

5. A flow rate control apparatus to be provided in a middle of a medical
solution injection path from a container accommodating medical solution
into a living body and capable of adjusting a flow rate of the medical
solution, the flow rate control apparatus comprising: a first substrate;
a second substrate, at least a part of the second substrate being bonded
to the first substrate; a third substrate, at least a part of the third
substrate being bonded to the second substrate; and a piezoelectric
material; wherein the first substrate includes a separation section
having a thickness equivalent to a thickness of the first substrate where
the first substrate is bonded to the second substrate, first and second
flow paths are formed in the first substrate, the first flow path and the
second flow path being separated from each other by the separation
section, the piezoelectric material is adhered to a position on a surface
of the second substrate, the position corresponding to a position of the
separation section, the surface being opposite to a surface facing the
first substrate, the piezoelectric material facing a piezoelectric
material in the third substrate via a gap, and the first substrate is not
bonded to the second substrate near the separation section.

6. A pump apparatus to be provided in a middle of a medical solution
injection path from a container accommodating medical solution into a
living body and capable of adjusting a flow rate of the medical solution,
the pump apparatus comprising: a first substrate; a second substrate, at
least a part of the second substrate being bonded to the first substrate;
and piezoelectric materials; wherein the first substrate includes first
and second separation sections, each of the sections having a thickness
equivalent to a thickness of the first substrate where the first
substrate is bonded to the second substrate, first and second flow paths
and a liquid chamber are formed in the first substrate, the first flow
path and the liquid chamber being separated from each other by the first
separation section, the liquid chamber and the second flow path being
separated from each other by the second separation section, the
piezoelectric materials are adhered to respective positions on a surface
of the second substrate, the respective positions corresponding to
positions of the first separation section, the second separation section,
and the liquid chamber, the surface being opposite to a surface facing
the first substrate, and the first substrate is not bonded to the second
substrate near the first separation section and the second separation
section.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority under 35 U.S.C §119
based on Japanese Patent Application No. 2010-024256 filed Feb. 5, 2010,
the entire contents of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to a flow rate control
apparatus and a pump apparatus. More particularly, the present invention
relates to a flow rate control apparatus and a pump apparatus preferably
adapted to adjust an injection amount (flow rate) of a medical solution
to be injected from a container accommodating the medical solution into a
living body.

[0004] 2. Description of the Related Art

[0005] Generally, an infusion apparatus is used when it is necessary to
inject a medical solution into a living body. In such an injection
apparatus, one end of a tube is connected to a container (transfusion
container) accommodating a medical solution, and the other end of the
tube is connected to an injection needle so that the medical solution can
be injected into a living body. Further in the middle of the tube, there
is provided a flow rate control apparatus to adjust the injection rate of
the medical solution.

[0006] In the description, it is assumed that the term "living body" is
not limited to human beings (human bodies) but broadly includes bodies of
animals; that the term "into a living body" broadly includes into a vein
and an organ of the living body; and that the term "medical solution"
(which may also be called "transfusion") broadly includes a liquid
medicine, and a liquid to be injected into a living body via a tube and
the like.

[0007] Conventionally, to control the flow rate of a medical solution to
be injected into a living body, a method using a device including an
infusion tube and a clamp is widely used. In most cases, a medical staff
member such as a nurse may operate the clamp while watching a drip state
of the medical solution in the infusion tube. However, in this method, an
operator such as the medical staff member may have to adjust the clamp
based on his/her experiences and/or intuition.

[0008] More specifically, the operator may have to determine the drip
state of the medical solution by carefully observing the size of the
liquid droplets dropping in the infusion tube and the number of the
liquid droplets per unit time period observed. Because of this feature,
in this method, it may be difficult especially for a less-experienced
operator to determine an appropriate flow rate of a medical solution to
be injected into a living body.

[0009] Besides the above method, there is a known apparatus which is
called an infusion pump. In the infusion pump, an appropriate flow rate
(a flow amount per unit time period, i.e., injection amount) is adjusted
by using a motor to drive a syringe, the motor having a mechanism in
which the number of revolutions can be controlled or by using a
peristaltic pump that presses a tube.

[0010] For example, Japanese Patent Application Publication No.
2002-126092 (Patent Document 1) discloses a self-contained type
transfusion system capable of controlling a dose (injection) amount of a
medical solution such as insulin to be injected at lower flow rates. In
the transfusion system, to control the flow rate, a piezoelectric valve
is operated to be opened and closed periodically and feedback control is
performed using a signal from a thermal flow rate sensor.

[0011] However, the technique described in Patent Document 1 is adapted to
control a smaller amount of medical solution such as a case of dosing
insulin. Further, due to the configuration of the transfusion system, the
transfusion system is used for normal (small) transfusions. Because of
this limitation, the technique described in Patent Document 1 may be
difficult to be adapted to control the flow rate ranging, for example,
from 100 ml/hr to 300 ml/hr. Further, in the technique described in
Patent Document 1, a plastic film is used as the valve and the
configuration of the system becomes complicated. Therefore, it may be
difficult to assemble the system.

SUMMARY OF THE INVENTION

[0012] The present invention is made in light of the above circumstances,
and may provide a flow rate control apparatus and a pump apparatus
capable of adjusting a flow rate to up to a desired flow rate usually set
in normal (typical) transfusions with a simpler configuration.

[0013] According to an aspect of the present invention, there is provided
a flow rate control apparatus to be provided in a middle of a medical
solution injection path from a container accommodating medical solution
into a living body and capable of adjusting a flow rate of the medical
solution. The flow rate control apparatus includes a first substrate; a
second substrate, at least a part of the second substrate being bonded to
the first substrate; and a piezoelectric material. In the flow rate
control apparatus, the first substrate includes a separation section
having a thickness equivalent to a thickness of the first substrate where
the first substrate is bonded to the second substrate; first and second
flow paths are formed in the first substrate, the first flow path and the
second flow path being separated from each other by the separation
section; the piezoelectric material is adhered to a position on a surface
of the second substrate, the position corresponding to a position of the
separation section, the surface being opposite to a surface facing the
first substrate; and the first substrate is not bonded to the second
substrate near the separation section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other objects, features, and advantages of the present invention
will become more apparent from the following description when read in
conjunction with the accompanying drawings, in which:

[0015]FIG. 1 is a schematic drawing illustrating a configuration of a
flow rate control apparatus according to an embodiment of the present
invention;

[0016]FIG. 2 is a schematic drawing illustrating the configuration of the
flow rate control apparatus when a control flow path is opened;

[0017]FIG. 3A is a top view of a first substrate in an area defined by a
dotted square of FIG. 1;

[0018]FIG. 3B is a top view of the flow rate control apparatus in the
area defined by the dotted square of FIG. 1;

[0019] FIG. 4A is a cross-sectional view cut long line A-B of FIG. 3B;

[0020] FIG. 4B is a cross-sectional view cut long line A-B of FIG. 3B when
the control flow path is opened;

[0026]FIG. 7B is a cross-sectional view cut long line A-B of FIG. 6 when
the control flow path is opened;

[0027]FIG. 8A is a schematic cross-sectional view of a pump apparatus in
a non-driven state according to an embodiment of the present invention;

[0028]FIG. 8B is a schematic cross-sectional view of the pump apparatus
when liquid is being supplied to a liquid chamber;

[0029]FIG. 8C is a schematic cross-sectional view of the pump apparatus
when liquid is being discharged from the liquid chamber;

[0030]FIG. 9 is an schematic drawing of drive voltage waveforms applied
by the voltage application means of the pump apparatus; and

[0031] FIG. 10 is a schematic drawing illustrating an exemplary
configuration of a medical solution injection system according to an
embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] In the following, exemplary configurations according to an
embodiment of the present invention are described based on embodiments of
the present invention with reference to FIGS. 1 through 10.

Flow Rate Control Apparatus

[0033] A flow rate control apparatus according to an embodiment of the
present invention is connected (disposed) at the middle of a medical
solution injection path through which a medical solution flows from a
container accommodating the medical solution and is injected into a
living body.

[0034] Further, as schematically illustrated in FIG. 1, a flow rate
control apparatus 1 according to an embodiment of the present invention
includes a first substrate 2, a second substrate 3, and a piezoelectric
material 4. At least a part of the second substrate 3 is bonded to the
first substrate 2. The first substrate 2 includes a separation section
formed in a manner such that the separation section 9 has a thickness
(height) equivalent to the thickness of the first substrate 2 where the
first substrate 2 is bonded to the second substrate 3. Further, a first
flow path 5a and a second flow path 5b are formed (defined) in the first
substrate 2 in a manner such that the first flow path 5a and the second
flow path 5b are separated from each other by the separation section 9.
Further, the piezoelectric material 4 is adhered to (provided on) an area
on a surface of the second substrate 3, the surface being opposite to the
surface facing the first substrate 2, and the area corresponding to the
separation section 9 of the first substrate 2. Further, the first
substrate 2 and the second substrate 3 are not bonded to each other in
the area near the separation section 9.

[0035] More detail of the flow rate control apparatus 1 according to an
embodiment of the present invention is described with reference to FIGS.
1 through 4.

[0036]FIG. 1 schematically illustrates an exemplary configuration of the
flow rate control apparatus 1. FIG. 2 illustrates a status where a
control flow path is opened (described below) of the flow rate control
apparatus 1 of FIG. 1. FIGS. 3A and 3B are top views of the area
indicated by the dotted lines (square) of FIG. 1. FIGS. 4A through 4D are
cross-sectional views cut along the corresponding lines illustrated in
FIG. 3B.

[0037] As illustrated in FIG. 1 and as described above, groove-shaped flow
paths 5a and 5b serving as flow paths to perform transfusions are formed
in the first substrate 2. Further, through holes 6a and 6b are formed
through the first substrate 2 so that the flow paths 5a and 5b are in
communication with the outside of the first substrate 2 through the
through holes 6a and 6b, respectively.

[0038] Further, as described above, a middle part (i.e., separation
section 9, detail is described below) formed between the flow path 5a and
the flow path 5b along the longitudinal direction of the flow paths 5a
and 5b is formed so as to have a thickness equivalent to the thickness of
the first substrate 2 surrounding the middle part.

[0039] Preferably, the first substrate 2 may be, for example, a
single-crystal silicon substrate. Further, the flow paths 5a and 5b and
the through holes 6a and 6b may be formed by performing, for example,
photolithography and etching on the silicon substrate.

[0040] As described above, the second substrate 3 is partially bonded to
the first substrate 2. Preferably, the second substrate 3 may be, for
example, made of borosilicate glass having a coefficient of thermal
expansion equivalent to that of silicon. Further, preferably, the first
substrate 2 and the second substrate 3 may be bonded to each other based
on, for example, anodic bonding.

[0041] In this case, specifically, a polished surface of the borosilicate
glass substrate to be bonded and a polished surface of the silicon
substrate to be bonded are in contact with each other, and heat and
voltage are applied to the contacting surfaces so as to generate covalent
bonding. As a result, those surfaces of first and second substrates are
strongly bonded to each other.

[0042] Further, as described above, the piezoelectric material 4 is
adhered to the area on a surface of the second substrate 3, the surface
being opposite to a surface facing (being contact with) the first
substrate 2, the area corresponding to the separation section 9 (i.e.,
above the separation section 9 in FIG. 1). As the piezoelectric material
4, it may be preferable to use PZT (Lead Zirconate Titanate).

[0043] Though it is not shown in FIG. 1, an electrode 8 is formed on the
second substrate 3 (between the second substrate 3 and the piezoelectric
material 4), and another electrode 8 is also formed on a surface of the
piezoelectric material 4, the surface being opposite to the surface on
the second substrate 3 side (see FIG. 4). The electrodes 8 may be formed
based on the sputtering method, the evaporation method or the like.
Further, the electrodes 8 are connected to external voltage application
means (not shown).

[0044] Regarding the bonding between the first substrate 2 and the second
substrate 3, due to the anodic bonding or the like, the first substrate 2
is strongly bonded to the second substrate 3 in the (contacting) area
other than the area which is under the piezoelectric material 4 (i.e.,
the area other than the area near the separation section 9). In other
words, in the area near (above) the separation section 9, there is in a
state where the first substrate 2 and the second substrate 3 are not
bonded to each other unlike the other area where the first substrate 2
and the second substrate 3 are strongly bonded to each other based on,
for example, anodic bonding.

[0045] Herein, the term "the state where the first substrate 2 and the
second substrate 3 are not bonded to each other" refers to a not only
where the first substrate 2 is in contact with the second substrate 3 but
also where there is temporary adhesion between the first substrate 2 the
second substrate 3, but when the second substrate 3 is bent due to
displacement (bent) of the piezoelectric material 4, the adhesion is
released. Further, the term an area "near the separation section 9" does
not always include the entire separation section 9. Namely, the area
"near the separation section 9" refers to an area which is determined so
that when a control flow path 7 is formed due to the bending of the
second substrate 3 (described below), the control flow path 7 establishes
communication between the flow path 5a and the flow path 5b.

[0046] The configuration may be achieved by, for example, forming an
adhesion area where the first substrate 2 is temporary adhered to the
second substrate 3 near the separation section 9. To achieve the
temporary adhesion, the surfaces of the adhesion area may be formed as a
rough surfaces by etching or the like. Otherwise, for example, the
temporary adhesion may be achieved by inserting a different material such
as a silicon oxide film, a silicon nitride film or the like between the
first substrate 2 and the second substrate 3 in a process of performing
the anodic bonding or the like between the second substrate 3 and the
first substrate 2.

[0047] By having the configuration of the flow rate control apparatus 1,
when a voltage is applied by the voltage application means via the
electrodes 8 to the piezoelectric material 4 which is adhered to the
second substrate 3, it may become possible to displace (bend) the
piezoelectric material 4 in the d31 direction as illustrated in FIG. 2.
In this case, the piezoelectric material 4 extends its length in its
longitudinal direction.

[0048] Further, as described above, near the separation section 9, there
is an area where the first substrate 2 and the second substrate 3 are not
bonded to each other. As a result, due to the displacement (bending) of
the piezoelectric material 4, the second substrate 3 which is adhered to
the piezoelectric material 4 is accordingly displaced in the longitudinal
direction, thereby bending the second substrate 3.

[0049]FIG. 2 schematically illustrates the flow rate control apparatus 1
where the second substrate 3 is bent (displaced). Due to the bending of
the second substrate 3, the first substrate 2 and the second substrate 3
are separated from each other. As a result of the separation, a gap
(space) (i.e., the control flow path 7) is formed between the first
substrate 2 and the second substrate 3.

[0050] For example, a case is described where the flow rate control
apparatus 1 having the configuration as illustrated in FIGS. 1 and 2 is
disposed in a manner such that the near side in the figures (where the
flow path 5a and the through hole 6a are formed) is disposed at a
position higher in the vertical direction (higher pressure) than the
position (lower pressure) of the far side in the figures (where the flow
path 5b and the through hole 6b are formed).

[0051] In this case, by changing the status of the flow rate control
apparatus 1 from a state where no voltage is applied as illustrated in
FIG. 1 (which may be referred to as "a non-application state") to a state
where a voltage is being applied as illustrated in FIG. 2 (which may be
referred to as "a voltage application state"), it may become possible to
cause a medical solution or the like to flow from the through hole 6a to
the through hole 6b via the flow path 5b, the control flow path 7, and
the flow path 5b in this order.

[0052] As described above, by having (forming) the control flow path 7, it
may become possible to change (vary) the fluid resistance of a medical
solution in the flow rate control apparatus 1, thereby enabling
controlling the flow rate of the medical solution. In other words, the
first substrate 2 (more specifically, the separation section 9) and the
part of the second substrate 3 corresponding to (facing) the separation
section 9 may serve as a valve.

[0053] Specifically, in the non-application state, the first substrate 2
(i.e., the separation section 9) is in contact with the second substrate
3 (i.e., the valve is closed ("closed valve state")) and the fluid
resistance is higher. Next, a voltage is applied to displace (deform) the
second substrate 3 to expand the gap formed between the first substrate 2
and the second substrate 3 (i.e., the valve is opened ("opened valve
state")). As a result, the fluid resistance may be reduced.

[0054] In this case, needless to say, it is not always necessary that a
value of the flow rate be set to "0" in the non-application state. It may
be applicable as long as at least a predetermined difference can be
generated (obtained) between the non-application state and the voltage
application state.

[0055] Further, in this embodiment, an etching process has been performed
on the area corresponding to the separation section 9 of the first
substrate 2, so that a small flow rate may be generated from the side
having higher pressure to the side having lower pressure.

[0056] Further, in the flow rate control apparatus 1 according to this
embodiment of the present invention, the flow path that may be in contact
with a medical solution is exclusively made of the single-crystal silicon
substrate 2 or the borosilicate glass substrate 3. Because of this
feature, no organic matter may be dissolved into the medical solution and
high safety may be achieved. Further, in case of an abnormal condition
such as electric power failure, a transfusion flow may be better
controlled and high safety may also be achieved.

[0057] As an example of the flow rate control apparatus 1, the thickness
of the borosilicate glass substrate 3, and the thickness of the PZT-5A
material as the piezoelectric material 4 are set to 150 μm and 0.2 mm,
respectively, and the sizes of the flow rate control apparatus 1 are set
to 2 mm (lateral) by 10 mm (vertical).

[0058] In this configuration, when a drive voltage 70 V is applied, a
displacement of 4 μm is obtained. Further, under the condition that
the height difference between the transfusion container and the flow rate
control apparatus 1 is 70 cm, the flow rates of 400 ml/hr and 40 ml/hr in
the "opened valve state" in FIG. 2 and the "closed valve state" in FIG.
1, respectively, are obtained.

Duty Control

[0059] As described above, in a flow rate control apparatus 1 according to
an embodiment of the present invention, by performing control to select
one of no voltage being applied and voltage being applied, a state where
a valve is closed and a state where the valve is opened, respectively,
may be generated. In other words, the fluid resistance may be changed by
performing a two-value control to generate the "closed valve state" and
the "opened valve state".

[0060] Because of this feature, by performing a further control of
adjusting the time periods of the "closed valve state" and the "opened
valve state", it may become possible to acquire a desired flow rate. In
this case, the flow rate may be changed depending on the height
difference between the transfusion container and the flow rate control
apparatus 1. Therefore, it may be necessary to consider the height
difference when controlling the time periods to acquire a desired flow
rate.

[0061]FIG. 5 schematically illustrates drive voltage waveforms
(representing respective duty ratios D) to be applied to the electrodes 8
of the flow rate control apparatus 1, the voltage waveforms being
generated by the voltage application means. The duty ratio D is a ratio
of the pulse width (i.e., ratio of a high level period to a single cycle
period). By changing the duty ratio D by applying a drive pulse having a
predetermined cycle period, it may become possible to increase (change) a
time period "t" of the "opened valve state", thereby enabling increasing
the flow rate.

[0062]FIG. 5 illustrates cases of the flow rates of the minimum flow rate
(0%), 25%, 50%, 75%, and the maximum flow rate (100%). For example, when
assuming that the drive cycle is 2000 Hz, by changing the duty ratio D,
it may become possible to control the flow rate in a range from 50 ml/hr
(as the minimum flow rate) to 300 ml/hr (as the maximum flow rate).

[0063] In the above description, a method is described in which the flow
rate is controlled by changing the duty ratio D while the voltage is
constant. However, the control method of controlling the flow rate is not
limited to the method. For example, a desired flow rate may be obtained
by changing (adjusting) the flow rate based on the pulse interval
modulation (with a constant voltage) in which the pulse interval between
the pulse widths having a constant width is changed. Otherwise, a desired
flow rate may be obtained by changing (adjusting) the flow rate by
changing the applied voltage (drive voltage) value to change the
displacement amount. Further, for example, a desired flow rate may be
obtained by any combination of the above-described methods of controlling
the flow rate.

[0064] Further, for example, to obtain a desired flow rate, plural flow
rate control apparatuses 1 may be connected in series or in parallel in
the flow path(s) of the transfusion.

[0065] In the flow rate control apparatuses 1 according to this embodiment
of the present invention described above, the single-crystal silicon
substrate 2 and the borosilicate glass substrate 3 may be used as the
components of the valve, and an accurate valve function may be obtained
with a simple configuration.

[0066] Further, by controlling the time period to open the valve per a
constant cycle period, it may become possible to accurately control the
flow rate. Further, the control may be performed in a cycle period
ranging from several kHz to several tens of kHz. By doing this, it may
become possible to prevent the occurrence of pulsation phenomena in the
controlled flow.

[0067] Further, similar to a micro pump, the flow rate control apparatus
may be fabricated by using the MEMS (Micro Electro Mechanical Systems)
technique. Therefore, it may become possible to fabricate the flow rate
control apparatus at a low cost. Further, the piezoelectric material 4 is
used to generate the driving force to bend the second substrate 3.
Therefore, it may become possible to increase the speed of opening and
closing the valve, thereby enabling an accurate flow rate control.

Second Embodiment

[0068] Next, a flow rate control apparatus according to another (second)
embodiment of the present invention is described with reference to FIGS.
6 through 7B. The flow rate control apparatus according to this
embodiment of the present invention is connected (disposed) at the middle
of a medical solution injection path through which a medical solution
flows from a container accommodating the medical solution and is injected
into a living body.

[0069] Further, as schematically illustrated in FIGS. 6 through 7B, a flow
rate control apparatus 1 according to this embodiment of the present
invention includes a first substrate 2, a second substrate 3, a third
substrate 10 and the piezoelectric material 4. At least a part of the
second substrate 3 is bonded to the first substrate 2. The first
substrate 2 includes a separation section 9 which is formed in a manner
such that the separation section 9 has a thickness (height) equivalent to
a thickness of the first substrate 2 where the first substrate 2 is
bonded to the second substrate 3. Further, a first flow path 5a and a
second flow path 5b are formed (defined) in the first substrate 2 in a
manner such that the first flow path 5a and the second flow path 5b are
separated from each other by the separation section 9.

[0070] Further, an electrode 8 is formed at a position on a surface of the
second substrate 3, the surface of the second substrate 3 being opposite
to the surface facing the first substrate 2, the position corresponding
to the position of the separation section 9 of the first substrate 2, and
the position being opposite to an electrode of the third substrate 10 via
a gap (space) 12. Further, the first substrate 2 and the second substrate
3 are not bonded to each other near the separation section 9.

[0071]FIG. 6 is a top view of the first substrate 2. FIGS. 7A and 7B are
cross-sectional views cut along the line A-B of FIG. 6. In the
description of this second embodiment, the repeated descriptions of the
same elements as those described in the first embodiment may be omitted.

[0072] As schematically illustrated in FIG. 6, the flow paths 5a and 5b
and the through holes 6a and 6b are formed by performing photolithography
and etching on a single-crystal silicon substrate as the first substrate
2.

[0073] Further, as schematically illustrated in FIGS. 7A and 7B, the first
substrate 2 is bonded to the borosilicate glass substrate as the second
substrate 3 based on, for example, anodic bonding.

[0074] Further, in this embodiment, there is formed an area where the
first substrate 2 is not (strongly) bonded to the second substrate 3 so
that the control flow path 7 can be generated (formed) to bridge
(communicate) between the first flow path 5a and the second flow path 5b
when the second substrate 3 is bent (as described below). Further, the
electrode 8 made of aluminum or the like is formed on the (upper) surface
of the second substrate 3 and is connected to external voltage
application means (not shown).

[0075] Further, as schematically illustrated in FIGS. 7A and 7B, a
taper-shaped groove is formed on the third substrate 10. The groove on
the third substrate 10 may be formed by performing etching on a
single-crystal silicon substrate having a small specific resistance by
using a resist film having a changing gradient. By forming the groove,
the gap (space) 12 is formed between the second substrate 3 and the third
substrate 10.

[0076] Then an insulation film 11 is formed by thermal oxidation. Further,
etching is performed on insulation film 11 formed on a contacting surface
of the third substrate 10, so that anodic bonding is established between
the third substrate 10 and the borosilicate glass substrate as the second
substrate 3. Further, an electrode is formed in the third substrate 10
and is connected to external voltage application means (not shown).

[0077] In the configuration of the flow rate control apparatus 1 as
described above, when a voltage is applied between the electrode 8 of the
second substrate 3 and the third substrate 10, an electrostatic force is
generated between the electrode 8 of the second substrate 3 and the third
substrate 10, thereby deforming the second substrate 3 within the gap
(space) 12 in a manner such that the second substrate 3 approaches the
surface of the taper-shaped groove (as illustrated in FIG. 7B). Due to
the deformation of the second substrate 3, the control flow path 7 is
formed (generated) so that the medical solution can flow between the
first flow path 5a and the second flow path 5b (see FIG. 7B).

[0078] Herein, in the example indicated in FIGS. 6 through 7B, in order to
make it easier to bend (displace) the second substrate 3, it is
preferable that the thickness of the borosilicate glass (i.e., the second
substrate 3) be in a range, for example, from 50 μm to 100 μm.
Further, for example, when the voltage (drive voltage) is 100 V, the
displacement is 5 μm and the width and the length of the formed
(generated) control flow path 7 are 3 mm and 10 mm, respectively.
Further, when the height difference between the transfusion container and
the flow rate control apparatus 1 is 70 cm, the flow rate in the "opened
valve state" indicated in FIG. 7B is 400 ml/hr and the flow rate in the
"closed valve state" indicated in FIG. 7A is 30 ml/hr (when the driving
cycle is 2000 Hz).

[0079] Further, in this embodiment, a case is described where the groove
to be formed on the third substrate 10 is taper-shaped and is not a
non-parallel shape. However, the shape of the groove is not limited to
this shape. For example, the groove may have any shape such as a parallel
shape (i.e., a cuboid shape). In a case where the groove has a parallel
shape, it is preferable that a drive voltage to be applied be higher than
that applied when the groove has a non-parallel shape.

[0080] As described above, in the flow rate control apparatus 1 according
to this embodiment of the present invention, by forming (generating) the
control flow path 7, it may become possible to change the fluid
resistance of the transfusion (medical solution). Namely, by using the
silicon substrate as the third substrate 10 and the borosilicate glass
substrate as the second substrate 3, an electrostatic actuator may be
configured (formed).

[0081] Due to the electrostatic force generated between the second
substrate 3 and the third substrate 10, the second substrate 3 may be
displaced, thereby enabling opening and closing the valve to control the
flow rate. Further, the surfaces to be in contact with the transfusion
fluid in the flow paths are made of single-crystal silicon, a silicon
oxide film, or a silicon nitride film, which are chemical compounds of
the single-crystal silicon; or the borosilicate glass only. Because of
this feature, no organic matter may be dissolved into the medical
solution and high safety may also be achieved.

Pump Apparatus

[0082] Next, a pump apparatus according to an embodiment of the present
invention is described with reference to FIGS. 8A through 9. A pump
apparatus in this embodiment includes a flow rate control apparatus 1
according to an embodiment of the present invention and a micro diaphragm
having a piezoelectric device as a drive source. Namely, a pump apparatus
20 according to this embodiment is connected (disposed) at the middle of
a medical solution injection path through which a medical solution flows
from a container accommodating the medical solution and is injected into
a living body, so as to adjust the flow rate of the medical solution.

[0083] As schematically illustrated in FIGS. 8A through 8C, the pump
apparatus 20 includes a first substrate 22 and a second substrate 23. At
least a part of the second substrate 23 is bonded to the first substrate
22. The first substrate 22 includes a first separation section 29a and a
second separation section 29b which are formed in a manner such that the
separation sections 29a and 29b have a thickness (height) equivalent to a
thickness of the first substrate 22 where the first substrate 2 is bonded
to the second substrate 23.

[0084] Further, a first flow path 25a, a liquid chamber 31, and a second
flow path 25b are formed (defined) in the first substrate 22 in a manner
such that the first flow path 25a and the liquid chamber 31 are separated
from each other by the first separation section 29a and the liquid
chamber 31 and the second flow path 25b are separated from each other by
the second separation section 29b. Further, piezoelectric materials 24a,
24b, and 24c are adhered to the second substrate 23 at their respective
positions on a surface of the second substrate 23, the surface of the
second substrate 23 being opposite to the surface facing the first
substrate 22, the respective positions corresponding to the positions of
the first separation section 29a, the second separation section 29b, and
the liquid chamber 31, respectively.

[0085] Further, the first substrate 22 and the second substrate 23 are not
bonded to each other near the first separation section 29a and the second
separation section 29b. In the description of this embodiment, the
repeated descriptions of the same elements as those described in the
above flow rate control apparatus 1 may be omitted.

[0086] FIGS. 8A through 8C schematically illustrate an exemplary
configuration of the pump apparatus 20. As schematically illustrated in
the figures, in the pump apparatus 20, the first flow path 25a, the
liquid chamber 31, and the second flow path 25b are formed (defined) by
performing etching on a silicon substrate as the first substrate 22.

[0087] Further, the borosilicate glass substrate as the second substrate
23 is partially bonded to the first substrate 22 based on anodic bonding.
Further, above the positions corresponding to the positions of the first
separation section 29a and the second separation section 29b, the
electrodes 28a and 28b, respectively, are formed. Then, the piezoelectric
materials 24a and 24b are adhered to (formed on) the electrodes 28a and
28b, respectively. Then electrodes 28a and 28b are formed on the
piezoelectric materials 24a and 24b, respectively. In the same manner, an
electrode 28c and the corresponding piezoelectric material 24c are
formed. Further, a valve 21 and a pump unit 30 may be fabricated in the
same manner as described above.

[0088] Herein, a first valve 21a and a second valve 21b have the same
configuration as that of the valve of the flow rate control apparatus 1
described above. Namely, in the bonding between the first substrate 22
and the second substrate 23, the first substrate 22 and the second
substrate 23 are strongly bonded to each other based on, for example,
anodic bonding in the area other than areas near the first separation
section 29a and the second separation section 29b which correspond to the
areas under the piezoelectric materials 24a and 24b, respectively. On the
other hand, unlike the areas where the first substrate 22 and the second
substrate 23 are bonded to each other, the first substrate 22 and the
second substrate 23 are not bonded to each other in the areas near the
first separation section 29a and the second separation section 29b which
correspond to the areas under the piezoelectric materials 24a and 24b,
respectively.

[0089] Further, in the same manner, the pump unit 30 is connected to
voltage application means. By applying a voltage to the piezoelectric
material 24c in the pump unit 30 by the voltage application means, the
piezoelectric material 24c is displaced, thereby bending the second
substrate 23 adhered to the piezoelectric material 24c and changing the
capacity of the liquid chamber 31. Further, the operations of the pump
unit 30 are the same as those in a known micro diaphragm.

[0090] Further, a tube 32a connected to the transfusion container (medical
solution container) is connected to a through hole 26a of the first flow
path 25a, and a tube 32b connected to an output section (downstream side)
is connected to a through hole 26b of the second flow path 25b.

[0091]FIG. 8A schematically illustrates a state where the pump apparatus
20 is not being driven. In this state, a voltage is applied to the
piezoelectric material 24c provided above the liquid chamber 31, so that
the liquid chamber 31 is displaced (deformed). As a result, the volume
(capacity) of the liquid chamber 31 is accordingly increased, thereby
enabling absorbing (increasing) the liquid in the liquid chamber 31. At
the same time, a voltage is also applied to the piezoelectric material
24a of the first valve 21a, so that the valve (a control flow path 27a)
is opened to decrease the fluid resistance. By doing this, the medical
solution flows from the first flow path 25a on input side (upstream side)
into the liquid chamber 31 (see FIG. 8B).

[0092] Next, the application of the voltage to the piezoelectric material
24a of the first valve 21a is stopped, so that the first valve 21a (i.e.,
the control flow path 27a) is closed so as to increase the fluid
resistance. At the same time, the application of the voltage applied to
the piezoelectric material 24c provided above the liquid chamber 31 is
stopped, so as to increase the pressure in the liquid chamber 31 (to
return to its original state).

[0093] Then, a voltage is applied to the piezoelectric material 24b of the
second valve 21b so that the valve (a control flow path 27b) is opened to
decrease the fluid resistance. By doing this, the medical solution flows
from the liquid chamber 31 and is discharged to (injected into) the
second flow path 25b on the output side (downstream side) (see FIG. 8C).

[0094] Next, the drive control of the pump apparatus 20 is described in
more detail with reference to a timing chart of FIG. 9. Herein, it is
assumed that drive voltages to drive the first valve 21a, the pump unit
30, and the second valve 21b are represented by symbols E1, E2, and E3,
respectively.

[0095] First, in the state of FIG. 8A, the drive voltage E1 is applied to
the first valve 21a to open the first valve 21a. At the same time, the
drive voltage E2 is also applied to the pump unit 30 to displace (deform)
an upper wall of the liquid chamber 31 to increase the volume (capacity)
of the liquid chamber 31, so that the liquid solution is absorbed
(transferred) from the first flow path 25a on the input side into the
liquid chamber 31 (step S1: "liquid supply period", FIG. 8B).

[0096] Next, the drive voltage E1 is set to 0 V to close the first valve
21a. On the other hand, the drive voltage E2 is maintained to keep the
volume (capacity) of the liquid chamber 31 constant (step S2: "transition
period").

[0097] Next, the drive voltage E3 is applied to the second valve 21b to
open the second valve 21b and the drive voltage E2 to drive the pump unit
30 is reduced down to 0 V. Due to the rigidity of the upper wall of the
pump unit 30, the volume (capacity) of the liquid chamber 31 is returned
to its original value or the volume (capacity) of the liquid chamber 31
may be somewhat less than the original value due to the inward bending of
the second substrate 23 adhered to the piezoelectric material 24c.

[0098] Due to the decrease of the volume (capacity) of the liquid chamber
31, an internal pressure in the liquid chamber 31 is accordingly
increased. At this timing, the first valve 21a is closed. Therefore, the
liquid solution is discharged only into the second flow path 25b via the
second valve 21b (step S3: "liquid discharge period", FIG. 8C).

[0099] After that, an adjustment period having a predetermined time period
is provided to prevent the first valve 21a and the second valve 21b from
being opened at the same time. By having the adjustment period, it may
become possible to prevent the liquid solution from flowing out due to
external pressure (step S4: "transition period", FIG. 8A).

[0100] By repeating the procedure from step S1 to step S4, the pump
apparatus 20 pumps the transfusion fluid (medical solution) from the tube
32a on input (upstream) side to the tube 32b on output (downstream) side.
Further, by exchanging the functions of the first valve 21a and the
functions of the second valve 21b, the input side and the output side can
be exchanged and transfusion fluid may be pumped in the direction
opposite to the direction described above.

[0101]FIG. 9 illustrates a control method in which the efficiency in the
flow rate of the liquid solution (medical solution) may be maximized. In
this control method, in the "liquid supply period" (i.e., in the
operation for supplying liquid solution into the liquid chamber 31), if
the first valve 21a is not opened, liquid solution is not supplied from
the first flow path 25a to the liquid chamber 31. Further, in the "liquid
supply period", if the second valve 21b is opened, liquid solution on
output side may be supplied (returned) from the second flow path 25b to
the liquid chamber 31. As a result, the loss of the liquid supply may be
generated (increased) and the efficiency of the pumping function may be
accordingly reduced. However, if the time period when the first valve 21a
is not opened and/or the second valve 21b is opened is short enough when
compared with the total "liquid supply period", the medical solution may
be sufficiently supplied to the liquid chamber 31 in the pumping
operation.

[0102] In the same manner, in the "liquid discharge period" (i.e., in the
operation for discharging liquid solution from the liquid chamber 31) if
the second valve 21b is closed, liquid solution is not supplied from the
liquid chamber 31 to the second flow path 25b. Further, in the "liquid
discharge period", if the first valve 21a is opened, liquid solution in
the liquid chamber 31 may be supplied (returned) to the first flow path
25a (input side). As a result, the loss of the liquid supply may be
generated (increased) and the efficiency of the pumping function may be
accordingly reduced. However, if the time period when the second valve
21b is closed and/or the first valve 21a is opened is short enough when
compared with the total "liquid discharge period", the medical solution
may be sufficiently discharged from the liquid chamber 31 to the second
flow path 25b in the pumping operation.

[0103] Accordingly, even though there is a time period when the valves 21a
and 21b are not set so as to efficiently supply and discharge liquid
solution (medical solution), if the time period is short enough, the pump
apparatus 20 may successfully perform as the pump for supplying medical
solution.

[0104] The above-described pump apparatus 20 according to an embodiment of
the present invention serves as not only the flow rate control apparatus
but also the pump. Because of the additional feature of the pumping
function, it may become possible to pump (flow) transfusion fluid
(medical solution) even when there is no height difference between the
transfusion container and the flow rate control apparatus or the
transfusion container is disposed lower than the flow rate control
apparatus.

Medical Solution Injection System

[0105] The above-described flow rate control apparatus may be included in
a medical solution injection system according to an embodiment of the
present invention. FIG. 10 schematically illustrates a medical solution
injection system according to an embodiment of the present invention.

[0106] As illustrated in FIG. 10, a medical solution injection system 100
includes a transfusion container 110, an injection needle 130, an
attachment tool 140, a medical solution injection tube 150, and a medical
solution flow rate adjustment apparatus 200. The transfusion container
110 accommodates medical solution to be injected into a living body 120.
The injection needle 130 is to be inserted into the living body 120 to
inject the medial solution. The attachment tool 140 is provided in
between the medical solution injection tube 150 and the injection needle
130 to connect them. The medical solution injection tube 150 is provided
between the transfusion container 110 and the attachment tool 140 to flow
(transfer) the medical solution.

[0107] The medical solution flow rate adjustment apparatus 200 is provided
in the middle of the medical solution injection tube 150, and includes
the flow rate control apparatus 1, a flow rate sensor 210, a control unit
220, and a driving unit 230 which serves as the voltage application
means.

[0108] When medical solution is to be injected into a part (e.g., a vein)
of the living body 120, the transfusion container 110 is connected to an
end (input end) of the medical solution flow rate adjustment apparatus
200 via the medical solution injection tube 150. As the medical solution
injection tube 150, a flexible tube having high flexibility and high
self-extensibility is typically used. However, any tube having any
material and any shape may alternatively used as long as medical solution
can flow through the tube.

[0109] The medical solution injection tube 150 connected to the attachment
tool 140 is connected to the other end (output end) of the medical
solution flow rate adjustment apparatus 200 (as illustrated in FIG. 10).

[0110] In the medical solution flow rate adjustment apparatus 200, the
control unit (i.e., microcomputer) 220 performs feedback control on a
flow rate value detected (measured) by the flow rate sensor 210. As the
flow rate sensor 210, for example, a thermal mass flow rate sensor may be
used. Further, the output from the flow rate sensor 210 may be supplied
in a form of an analog voltage signal or a digital output signal based on
I2C, RS-232C or the like.

[0111] The control unit (i.e., microcomputer) 220 includes a CPU (Central
Processing Unit) 221, an A/D converter, and a PWM (pulse width
modulation) output. By having this configuration, for example, the CPU
221 compares a measured flow rate value as a signal from the flow rate
sensor 210 with a predetermined reference flow rate value by performing
the calculation based on the PID (proportional-integral-derivative)
algorithm using three elements: deviation, integral of the deviation, and
differential of the deviation to obtain a control value (such as drive
force data, PWM output). The obtained control data is output (supplied)
to the driving unit 230.

[0112] Based on the received control data calculated in the control unit
220, the driving unit 230 drives a power transistor to form (generate)
pulses corresponding to the received control data (output voltage) to
control (adjust) the flow rate to be set in the flow rate control
apparatus 1. By having the configuration described above, it may become
possible to control the flow rate in the flow rate control apparatus 1 in
a range, for example, from 50 ml/hr to 300 ml/hr by transmitting a signal
from the flow rate sensor 210 to the control unit 220 and performing the
feedback control based on the PID control (algorithm).

[0113] Further, by adequately setting, for example, a value of the height
difference and a width value of the flow path, it may become possible to
set a flow rate value less than 50 ml/hr and/or greater than 300 ml/hr.

[0114] Further, in a medical solution injection system, by having the pump
apparatus 20 according to an embodiment of the present invention instead
of having the flow rate control apparatus 1, it may become possible to
pump (flow) transfusion fluid (medical solution) even when there is no
height difference between the transfusion container and the injection
needle or the transfusion container is disposed lower than the injection
needle. Further, in this case, besides the pump apparatus 20, the same
components may be used and the same control method described above may be
used.

[0115] According to an embodiment of the present invention, a flow rate
control apparatus is provided in a middle of a medical solution injection
path from a container accommodating medical solution into a living body
and capable of adjusting a flow rate of the medical solution, the flow
rate control apparatus including a first substrate; a second substrate,
at least a part of the second substrate being bonded to the first
substrate; and a piezoelectric material, in which the first substrate
includes a separation section having a thickness equivalent to a
thickness of the first substrate where the first substrate is bonded to
the second substrate, first and second flow paths are formed in the first
substrate, the first flow path and the second flow path being separated
from each other by the separation section, the piezoelectric material is
adhered to a position on a surface of the second substrate, the position
corresponding to a position of the separation section, the surface being
opposite to a surface facing the first substrate, and the first substrate
is not bonded to the second substrate near the separation section.

[0116] Further, the first substrate may be made of single-crystal silicon,
and the second substrate may be made of borosilicate glass.

[0117] Further, the first substrate and the second substrate may be bonded
to each other based on anodic bonding in an area other than an area near
the separation section.

[0118] The flow rate control apparatus may further include a voltage
application unit that applies voltage to the piezoelectric material so
that duty control is performed by applying a predetermined voltage by the
voltage application unit.

[0119] According to an embodiment of the present invention, there is
provided a flow rate control apparatus to be provided in a middle of a
medical solution injection path from a container accommodating medical
solution into a living body and capable of adjusting a flow rate of the
medical solution. The flow rate control apparatus includes a first
substrate; a second substrate, at least a part of the second substrate
being bonded to the first substrate; a third substrate, at least a part
of the third substrate being bonded to the second substrate; and a
piezoelectric material. In the flow rate control apparatus, the first
substrate includes a separation section having a thickness equivalent to
a thickness of the first substrate where the first substrate is bonded to
the second substrate; first and second flow paths are formed in the first
substrate, the first flow path and the second flow path being separated
from each other by the separation section; the piezoelectric material is
adhered to a position on a surface of the second substrate, the position
corresponding to a position of the separation section, the surface being
opposite to a surface facing the first substrate, the piezoelectric
material facing a piezoelectric material in the third substrate via a
gap; and the first substrate is not bonded to the second substrate near
the separation section.

[0120] According to an embodiment of the present invention, there is
provided a pump apparatus to be provided in a middle of a medical
solution injection path from a container accommodating medical solution
into a living body and capable of adjusting a flow rate of the medical
solution. The pump apparatus includes a first substrate; a second
substrate, at least a part of the second substrate being bonded to the
first substrate; and piezoelectric materials. In the pump apparatus, the
first substrate includes first and second separation sections, each
having a thickness equivalent to a thickness of the first substrate where
the first substrate is bonded to the second substrate; first and second
flow paths and a liquid chamber are formed in the first substrate, the
first flow path and the liquid chamber being separated from each other by
the first separation section, the liquid chamber and the second flow path
being separated from each other by the second separation section; the
piezoelectric materials are adhered to respective positions on a surface
of the second substrate, the respective positions corresponding to
positions of the first separation section, the second separation section,
and the liquid chamber, the surface being opposite to a surface facing
the first substrate; and the first substrate is not bonded to the second
substrate near the first separation section and the second separation
section.

[0121] According to an embodiment of the present invention, it may become
possible to accurately control the flow rate with a simple configuration.

[0122] Although the invention has been described with respect to specific
embodiments for a complete and clear disclosure, the appended claims are
not to be thus limited but are to be construed as embodying all
modifications and alternative constructions that may occur to one skilled
in the art that fairly fall within the basic teaching herein set forth.